Recording wire



Patented June 3, 1952 RECORDING WIRE Harold W. Cobb, Baltimore, Md., assignon to l I v Armco Ohio Steel Corporation, a corporation of No Drawing. Application July 1, 1946, Serial No. 680,845

1 Claim.

My invention relates both to a stainless steel product and method. More particularly, it concerns a method of producing stainless steel ribbon or wire displaying superior magnetic qualities, and to the resulting product especially adapted to sound recording.

Among the objects of my invention is to provide a stainless steel wire or generally similar articledisplaying advantageous magnetic qualities, adapted for sound recording in the substantial absence of detrimental characteristic noises and as well, in the substantial absence of appreciable loss of sonic side bands, harmonics and the like which, while involving a comparatively low cost for material, displays long useful life, high resistance to corrosion, rust and decay both in ordinary atmospheres and when exposed to humid or salt air and upon contact with the human hand; which is comparatively readily drawn to proper dimensions, and which displays superior magnetic qualities including but not being limited to high coercive force, high permeability, good residual induction and suitable induction at maximum field strength.

Other objects, advantages and features of my invention will in part be obvious and in part pointed out hereinafter during the course of the following disclosure, the scope of the application of all of which will be more fully set forth in the claim at the end of this specification.

Accordingly, my invention resides in the several operational and procedural steps, in the relation of each of the same to certain of the others and in the timed sequence thereof, and as well, to the products into which the steels thus treated are subsequently fabricated, and in the processed metal itself.

As conducive to a more thorough understanding of my invention, it may be noted at this point that for several decades the suggestion has been made that perhaps sound tracks could, through appropriate magnetic technique, be transferred to and recorded upon a metal ribbon or wire; the

' sound track being established thereon for indefinite periods of time and then employed as a record for the reproduction of audible sound as and when desired. Moreover, as desired the sound track thus produced could, by the use of proper technique, be readily removed so that the wire would be conditioned for re-use and for the application of a new sound track thereon. The advantages of such technique are apparent in that it is extremely simple .and involves-a minimum outlay both in equipment and in space requirements. in recording apparatus and in the Wire ribbon or track itself. This combination of basic simplicity and low equipment cost extends over into the reproduction apparatus. The elimination of the necessity of a reproducing needle, as in mechanical and electrical reproduction, is accompanied by the removal of the source of annoyance which so frequently attends upon needle scratching.

To that extent, therefore, close adherence to .the original tonal quality is achieved. Fidelity in reproduction is, therefore, enhanced. Since the sound wires can be of .substantially indefinite length, the necessity of interruption to change records is in large measure eliminated. The ribbons being small, storage space is reduced to a minimum. The potentialities of such method of reproduction is thus instantly realized as being tremendous.

In its early stages of development, however, this magnetic technique was observed to carry with it a number of inherent and fundamental difliculties which had to be eliminated before the new technique could be fully exploited and utilized with appreciable satisfaction.

I find that one of the principal requirements of such wire or ribbon is that magnetically it must possess high coercive qualities. That is to say, it must immediately assume and retain the magnetism of recording and, in addition, there must be a substantial resistance to loss of magnetism in subsequent storage and the like. Otherwise, in the first place, the sounds of the higher frequencies will not be adequately assured and, in the second place, the record obtained will dissipate from the ribbon and there will be substantial loss of the sound message. Particularly where the reproduction of music is concerned even moderate leakage of magnetism is found to result in loss of the overtones and harmonies which are so essential to pleasing reproduction, and as well, the full-bodied tonal qualities .of the original source are not reproduced faithfully. Detrimental ground noises inherent to the metal itself I find accompany the use of alloys of many compositions. Therefore, a first requirement of metal tape or wire is that it have require magnetization during heat-treatment to obtain best results.

To illustrate, a high cobalt steel comprising an additive of aluminum and nickel displays high coercivity, but is very expensive and difficult to work, to the extent that its use for the intended purpose is impracticalw Moreover, it requires: working either" under cold or hot conditions or a combination thereof. This mechanical working is found in many instances to produce ap preciable and detrimental variations in the magnetic qualities of the metal.

effect of converting a part of the austenite into Finally, even in' those few instances where proper magnetic and mechanical properties are found-to'residein-thei alloys, they are observed to be extremely sensitive to corrosion resulting from even ordinary atmospheric conditions. alloys, are susceptible to attack when exposed tohumid or salt air conditions and when-they come frequently into contact with the human Animportantobject of my invention, therefore; is seen to comprise the elimination or sup pression-in substantial measure of the defects and-disadvantages attendant; upon the practice according to the prior art, andat the same time, 1 to; evolve a'i-method of'p'roducing and-to provide a corrosion-resistant sound wire having highly desirable magnetic properties including high 1 coercivity, and which while easily workable, re tainsto an extremely high degree of fidelity the magnetio soundtrack. imposed thereupon with minimum; ground noise in reproduction, together with a m'eth'od of producing such wire which involvesia minimum number of procedural steps and requires minimum"expenditure of time;

Pursuant: to the practice of myinvention, l

find that it is not enough that a Wire be capableofbeing; highly:magnetized. To illustrate; it is wellzrecognized' thati-n the case of certain metals,

, highmagnetisin can exist, such :highdegree of 1 magnetism being retained, however, only during with straightchrome alloys, only to besubjected to the disappointment of :finding them -to be un-- suited for my purpose-.-

From my iworkit appears that the grain size, orientation of grains and similar characteristics of 'the'ameta-l are'highly" important in achieving highlcoercivity. The required good grain size and the like are not found in the ordinary straightchromium grades of stainlesssteel. As

Well they displayed highly detrimental, charac teristic ground 'noises r on the other hand, thetrul steel, donot pos'sess'favorable magnetic qualities.

' Ih-generalsuch steels are'oons'ide'red-to be essen tially non magnetic. I I

Q With no' encouragement from either the" straightchroinium steels for the. austenitic' chro mium-ni'ckei stainless: steels, .I nevertheless: di-

rected my attention tochromilirmnickel stainlessstels of the metastable type; The phenomenon was displayed'b'y steels'of thisjgeneralitype upon proper correlation of the'concentrationsof chro- V mium, nickel, carbon, nitrogen,- etc., that the metal is comparatively-stable unless influencedbyextern'al forces, but which-upon theapplication of'such outside forces, is likely to undergo a: change of "structure. be the same great or small Particularly then, such y austenitic steels such as; them27 =chromium-nickel stainless ferrite. Apparently, the ferrite is in a critical size and'dispersionthroughout the metal because as noted above'theusual ferritic steel is inadequate for my purpose. It is to be noted, however, that the cold-treatment must be accomplished Without converting the entire mass of metal from austenite into a different phase.

Inaccordance with my invention, I process the steel by subjecting the same to treatment at subatmospheric temperatures. To this end, I immerse the metastable non-magnetic austenite stainless steel in a cold medium such as boiling liquidnitrogenor solid carbon dioxide. Amixture'of solid carbon dioxide-with some organic liquid such as acetone or-alcoholwas found-tobe entirely feasible. The" temperature was carried to as low as -200 C. Aftera suitable length of time'w'ithin which the steel waspermittedto reach the desired bath temperature itis'removed from the coolant and allowedto warm-to-room temperature. 7

Where desired, several successive cycles of cooling'andwarming are employed The resulting product is found to displayhigh coercivity, maximum'permeability, good residual induction: and suitable induction at maximum fieldstrength. Soundtrack wire of required uniform calibrated thickness and width readily is formed of the metal; Strong, cleartones are produced therefrom. Groundnoises-theretofore prevailing are substantially eliminated. Corrosion resistance of high-order is observed. 7

As modifications of the treating procedure given above; I may-combine thesub-atmospheric treatment with prior external stressing treat-- ments- -sueh as cold-Working, stress-relievingandthe li-ke.-- I find'that-withthe combined treat-" mentshighlysatisfactory results are likewise achieved! Further, I observethat a'combination quent external stressing as by cold-working and 1 stress-relieving. In all instances, I observehigh- 1y satisfactory results. The cold-working; and stress-relieving treatments apparently do not so change the form and dispersement of ferrite as to'detraet from the desired magneticproperties but, on the contrary, appear to-enhance-thesequalities-somewhat; i

Thus"=according to th'e practice" of my 'in'ven tron, a new,.satisfactory and simpletechniq'iie is evolved for imparting sound recording. qua-li ties "to' austenitic stainlesssteelsr- The methodis' simple and rapid; Requirement of skilled labor" is reduced-to a'minimum; 'S'o'ftoo, is the required investment in plant, spaceand equipment; The metal thils produ'ced is highly maglflEti, p0SS'S'- ins high coercivity, and is' admirably suited for 'us'e in the production and -storage of soundtracks. Itis highl'y'r'esistanf'to corrosion underallextremes'of 1 atmospheric conditions; It can be readily worked into required small dimensions with a minimum of efiort. In point of fact, it is entirely feasible to shape and dimension wire so that the final cold-working of the metal into its final dimensions will bring about the required conversion from metastable austenitic condition to partly ferritic condition, so that the required good magnetic qualities are thereby imparted.

The chrome-nickel steels which I employ dis: play high coercivity. Such steels are readily worked into a wire having a diameter of say 0.004 inch, or even smaller if desired. As much as 10,000 feet of such wire can be wound on spools operating at a linear feed obtaining of around two feet per second. Overtones and harmonies are reproduced with fidelity. Ground noises heretofore detracting appreciably from the use of wire record tapes are substantially eliminated. All these and many other highly practical results are achieved according to the practice of my invention.

It is apparent from the foregoing that once the broad aspects of my invention are disclosed, many embodiments will occur to those skilled in the art, all falling within the scope thereof. Moreover, many modifications of the embodiment herein described will suggest themselves to those skilled in this art. Accordingly, I intend that the foregoing description be construed as merely illustrative and not by way of limitation.

I claim:

A cold-worked and cold-treated stainless steel sound recording medium of about 0.004 inch maximum thickness characterized by its high coercive qualities, high residual induction and 'substantial freedom from ground noise, comprising metastable austenitic chromium-nickel stainless steel containing 16% to 19% chromium, 6% to 12% nickel, up to 0.30% carbon and remainder principally iron having a structure comprised of substantially uniform partially transformed grains achieved by cold-treatment at a temperature between about 0 C. and -200 C.

HAROLD W. COBB.

REFERENCES CITED The following references are of record in the file or this patent:

OTHER REFERENCES "Transactions of American Society for Steel Treating, vol. XIX, Am. Soc. for Steel Treating, Cleveland, Ohio, pages 501-552.

Alloys of Iron and Chromium, vol. II, Kinzel and Franks, 1st ed., 1940, McGraw-I-Iill Book 00., Inc., N. Y. C. Pages 338-340.

"Steel Processing, Nov. 1944, pp. 721 through 725.

Stainless steels," Thum, pages 118-119, 1935. 

